1. Technical Field
This device relates to lock cylinders that are used in door lock mechanisms. Lock cylinders are thread ably secured within the lock case within the door with a setscrew used to secure the cylinder in the case. The setscrew prevents rotation and removal of the cylinder from the case. It has been found, however, that if the cylinder is rotated under high input force the setscrew fails allowing the cylinder to be freely rotated and removed gaining access to the lock case and thus unlocking the door.
2. Description of Prior Art
Prior art devices directed to safety lock cylinders have employed a number of different mechanical approaches to secure the cylinder lock within the lock case, see for example U.S. Pat. Nos. 5,291,767, 5,551,736 and 5,577,408.
In U.S. Pat. No. 5,291,767 a protective lock cylinder mounting assembly is disclosed having a pair of lock cylinders wherein the lock cylinders are secured to one another and one of the cylinders has a hidden set screw that prevents unauthorized rotation of the interconnected cylinder locks.
U.S. Pat. No. 5,551,736 is directed to a dual lock set dead bolt assembly for cylinder locks wherein a novel transmission means that facilitates adjustment between two standard bracket lengths is disclosed.
U.S. Pat. No. 5,577,408 claims a security device for a cylinder lock that has an arm attached to the cylinder case and extends there beyond preventing the cylinder from being removed from the case. The cylinder lock cam extends from the lock cylinder and rotates when the lock is keyed. In lock position the lock engagement cam covers the mounting screw preventing removal of the arm.
Other prior art patents show a variety of lock cylinders and mechanisms, some of which have extended cover plates and interconnected rotary arms for interconnecting with various portions of the assembly, see U.S. Pat. Nos. 1,268,137,939, and 1,546,626 which are incorporated by reference thereto.
A security lock cylinder device that extends from the locking cam of the lock cylinder that acts to activate the locking mechanism. The security device extends beyond the lock cylinder threaded engagement surface to prevent removal of the cylinder from within the lock case. The security locking cam has a dual oppositely disposed activation and security pawls that upon keyed rotation will fall within the cylinder surface field for cylinder removal from the lock case for authorized users.